Chemical amendments for the stimulation of biogenic gas generation in deposits of carbonaceous material

ABSTRACT

Methods of stimulating biogenic production of a metabolic product with enhanced hydrogen content are described. The methods may include accessing a consortium of microorganisms in a geologic formation that includes a carbonaceous material. They may also include providing hydrogen and one or more phosphorous compounds to the microorganisms. The combination of the hydrogen and phosphorous compounds stimulates the consortium to metabolize the carbonaceous material into the metabolic product with enhanced hydrogen content. Also, methods of stimulating biogenic production of a metabolic product with enhanced hydrogen content by providing a carboxylate compound, such as acetate, to a consortium of microorganisms is described. The carboxylate compound stimulates the consortium to metabolize carbonaceous material in the formation into the metabolic product with enhanced hydrogen content.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11,399,099, filed Apr. 5, 2006, the entire disclosures of which areincorporated hereby by reference for all purposes.

BACKGROUND OF THE INVENTION

Increasing world energy demand is creating unprecedented challenges forrecovering energy resources, and mitigating the environmental impact ofusing those resources. Some have argued that the worldwide productionrates for oil and domestic natural gas will peak within a decade orless. Once this peak is reached, primary recovery of oil and domesticnatural gas will start to decline, as the most easily recoverable energystocks start to dry up. Historically, old oil fields and coal mines areabandoned once the easily recoverable materials are extracted. Theseabandoned reservoirs, however, still contain significant amounts ofcarbonaceous material. The Powder River Basin in northeastern Wyoming,for example, is still estimated to contain approximately 1,300 billionshort tons of coal. Just 1% of the Basin's remaining coal converted tonatural gas could supply the current annual natural gas needs of theUnited States (i.e., about 23 trillion cubic feet) for the next fouryears. Several more abandoned coal and oil reservoirs of this magnitudeare present in the United States.

As worldwide energy prices continue to rise, it may become economicallyviable to extract additional oil and coal from these formations withconventional drilling and mining techniques. However, a point will bereached where more energy has to be used to recover the resources thancan be gained by the recovery. At that point, traditional recoverymechanisms will become uneconomical, regardless of the price of energy.Thus, new recovery techniques are needed that can extract resources fromthese formations with significantly lower expenditures of energy andcosts.

One route for light hydrocarbon recovery that has received littlecommercial attention is biogenic conversion of carbonaceous materials ingeologic formations into methane. As noted above, large potentialsources of methane and other hydrocarbons with enhanced hydrogen contentare locked up in the carbonaceous materials in coal, residual oil, etc.In biogenic conversion, microorganisms in the formation treat thesecarbonaceous materials as a food source and metabolize them intometabolic intermediates and products, such as alcohols, organic acids,aromatic compounds, hydrogen and methane, among others.

In many formations, however, the environmental chemistry does not favorthe biogenic production of metabolic products like hydrogen and methane.In some of these formations, the presence of an inhibitor (e.g., saline)can prevent the microorganisms from metabolizing the carbonaceoussubstrate into the products. In other formations, the low concentrationof one or more compounds (e.g., nutrient compounds) in the formationenvironment can slow or stop biogenic production of the products. Instill other formations, a rise in concentration of a metabolicintermediate or product generated by an active consortium ofmicroorganisms can slow additional metabolic activity.

Thus, there remains a need to identify chemical compounds that effectthe rate of biogenic production of metabolic products by microorganismsin a formation environment. There also remains a need for methods ofintroducing chemical amendments to a geologic formation that willstimulate the biogenic production of the metabolic products. These andother needs are addressed by the present invention.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention include methods of stimulating biogenicproduction of a metabolic product with enhanced hydrogen content. Themethods may include accessing a consortium of microorganisms in ageologic formation that includes a carbonaceous material. The methodsmay also include providing hydrogen and one or more phosphorouscompounds to the microorganisms. The combination of the hydrogen andphosphorous compound stimulates the consortium to metabolize thecarbonaceous material into a metabolic product with enhanced hydrogencontent.

Embodiments of the invention also include additional methods ofstimulating biogenic production of a metabolic product with enhancedhydrogen content. The methods may include accessing a consortium ofmicroorganisms in a geologic formation that includes a carbonaceousmaterial and providing a carboxylate compound to the microorganisms. Thecarboxylate compound stimulates the consortium to metabolizecarbonaceous material in the formation into the metabolic product withenhanced hydrogen content.

Embodiments of the invention still also include methods of activating aconsortium of microorganisms in a geologic formation to produce ametabolic product with enhanced hydrogen content. The methods mayinclude accessing the consortium in the formation, and providing anacetate compound to the microorganisms. The acetate compound activatesthe consortium to metabolize carbonaceous material in the formation intothe metabolic product with enhanced hydrogen content.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the invention. The features and advantages ofthe invention may be realized and attained by means of theinstrumentalities, combinations, and methods described in thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method of introducing hydrogen andphosphorous amendment to microorganisms in geologic formations accordingto embodiments of the invention;

FIG. 2 is a flowchart illustrating a method of introducing carboxylatecompound amendment to microorganisms in geologic formations according toembodiments of the invention;

FIG. 3 is a flowchart illustrating a method of measuring the effects ofintroduced amendments on the production of metabolic products fromgeologic formations according to embodiments of the invention;

FIG. 4 is a plot that compares methane concentrations in an unamendedsample with a sample treated with an acetate amendment;

FIG. 5 is a plot showing acetate concentration over time in sampleswhere an acetate amendment has been introduced;

FIG. 6 is a plot of methane concentration over time in an unamendedsample, and samples amended with a phosphorous compound or ammonia: and

FIG. 7 is a plot of methane concentration over time in an unamendedsample, and samples amended with a phosphorous compound or a mineralcomposition.

DETAILED DESCRIPTION OF THE INVENTION

Methods of stimulating the production of metabolic products withenhanced hydrogen content (e.g., gases such as hydrogen and methane)through chemical amendments are described. The amendments stimulate aconsortium of microorganisms in a geologic formation to metabolizecarbonaceous material in the formation into the metabolic products. Thestimulation effects of the amendments may include increasing the rate ofproduction of a metabolic intermediary and/or the metabolic product.They may also include activating a consortium in the formation to startproducing the metabolic products. They may further include stopping ordecreasing a “rollover” effect such as when the concentration of one ormore metabolic products starts to plateau after a period ofmonotonically increasing. These and other stimulation effects may bepromoted by the chemical amendments that are introduced by the methodsof the invention.

Referring now to FIG. 1, a flowchart illustrating a method 100 ofintroducing hydrogen and phosphorous amendments to microorganisms in ageologic formation according to embodiments of the invention is shown.The method 100 includes accessing the formation water 102 in thegeologic formation. The geologic formation may be a previously explored,carbonaceous material-containing subterranean formation, such as a coalmine, oil field, natural gas deposit, carbonaceous shale, etc. In manyof these instances, access to the formation can involve utilizingpreviously mined or drilled access points to the formation. Forunexplored formations, accessing the formation may involve digging ordrilling thorough a surface layer to access the underlying site wherethe microorganisms are located.

Once access to the microorganisms in the formation is available, anamendment may be provided to them. In method 100, providing theamendment may include providing hydrogen to the microorganisms 104.Providing the hydrogen 104 may involve the direct injection of hydrogengas into the formation region were the microorganisms are located.Alternatively (or in addition) a liquid and/or aqueous hydrogen releasecompound may be provided to the formation. The compound can undergo achemical or biochemical reaction in the formation that produces hydrogengas in situ where the microorganisms reside. Examples of hydrogenrelease compounds may include polyacetate ester compounds that releaselactic acid on contact with water. The lactic acid may then bemetabolized by the microorganisms to produce organic acids (e.g.,pyruvic acid, acetic acid, etc.) and hydrogen gas.

The amendment may also include providing one or more phosphorouscompounds to the microorganisms 106. These phosphorous compounds mayinclude phosphorous compounds (e.g., PD_(x) compounds were x is 2, 3 or4), such as sodium phosphate (Na₃PO₄) and potassium phosphate (K₃PO₄),as well as monobasic and dibasic derivatives of these salts (e.g.,KH₂PO₄, K₂HPO₄, NaH₂PO₄, Na₂HPO₄, etc.). They may also includephosphorous oxyacids and/or salts of phosphorous oxyacids. For example,the phosphorous compounds may include H₃PO₄, H₃PO₃, and H₃PO₂phosphorous oxyacids, as well as dibasic sodium phosphate and dibasicpotassium phosphate salts. The phosphorous compounds may also includealkyl phosphate compounds (e.g., a trialkyl phosphate such as triethylphosphate), and tripoly phosphates. The phosphorous compounds mayfurther include condensed forms of phosphoric acid, includingtripolyphosphoric acid, pyrophosphoric acid, among others. They may alsoinclude the salts of condensed phosphoric acids, including alkali metalsalts of tripolyphosphate (e.g., potassium or sodium tripolyphosphate),among other salts.

The hydrogen and phosphate may be provided to the formation in a singleamendment, or they may be provided in separate stages. For example, ifthe phosphorous amendment takes the form of an aqueous solution, thesolution may be injected into the formation with aid of compressedhydrogen gas. This allows the two components to be provided to theformation at substantially the same time. Alternatively, the hydrogen orphosphate amendment may be introduced first, followed by theintroduction of the other compounds.

Whether the hydrogen and phosphorous compounds are introduced to theformation simultaneously or separately, they will be combined in situand exposed to microorganisms. The combination of the hydrogen andphosphorous compound(s) can stimulate the microorganisms to metabolizecarbonaceous material in the formation into metabolic products withenhanced hydrogen content, like methane. The enhanced hydrogen contentproducts have a higher mol. % of hydrogen atoms than the startingcarbonaceous material. For example, methane, which has four C—H bondsand no C—C bonds, has a higher mol. % hydrogen than a large aliphatic oraromatic hydrocarbon with a plurality of C—C single and double bonds.Additional details about compounds with enhanced hydrogen content may befound in co-assigned U.S. patent application Ser. No. 11/099,881, toPfeiffer et al, filed Apr. 5, 2005, and entitled “GENERATION OFMATERIALS WITH ENHANCED HYDROGEN CONTENT FROM ANAEROBIC MICROBIALCONSORTIA” the entire contents of which is herein incorporated byreference for all purposes.

Method 100 may further include adding additional amendments to the toformation. For example, a yeast extract amendment may be added toprovide nutrients to the microorganisms in the formation. The yeastextract may include digests and extracts of commercially availablebrewers and bakers yeasts.

Method 100 may also include measuring the concentration of a metabolicproduct 108. For gas phase metabolic products, the partial pressure ofthe product in the formation may be measured, while aqueous metabolicproducts may involve measurements of molar concentrations. FIG. 1 showsthe measurement of metabolic products being made after the introductionof the hydrogen and phosphorous amendment. Measurements may also be madebefore providing the amendment, and a comparison of the productconcentration before and after the amendment may also be made.

FIG. 2 shows a method 200 of introducing a carboxylate compoundamendment to microorganisms in geologic formations according toembodiments of the invention. The method 200 may include accessing themicroorganism in the geologic formation 202. Once access is gained, oneor more carboxylate compounds may be provided to the microorganisms insitu 204. The carboxylate compound may be an organic compound having oneor more carboxylate groups (e.g., COO⁻ groups). These compounds aretypically organic acids or their salts. Examples include salts ofacetate (i.e., H₃CCOO⁻); benzoate (i.e., Ph-COO⁻, where Ph is a phenylgroup); and formate (i.e., HCOO⁻), among other carboxylate groups.Additional amendments, such as a yeast extract amendment that providesnutrients to the microorganism in the formation, may also be provided.

The concentration of a metabolic product may be measured 206 followingthe introduction of the carboxylate compound. The product concentrationmay also be measured before the carboxylate compound is introduced, todetermine the effect of adding the compound. In some instances,introducing the carboxylate compound to the microorganisms may cause analmost immediate increase in the production rate of the metabolicproduct. In other instances, there may be a period of delay between theintroduction of the carboxylate compound and an increase in theproduction of the metabolic product. For example, the concentration ofthe metabolic product in the formation may stay at pre-introductionlevels for about 30, 40, 50, 60, 70, or 80 days or more beforesignificantly increasing.

A delay of several days or months between introducing the carboxylatecompound and measuring a increase in the production of the metabolicproduct may be called the activation period. During this time, thepresence of the carboxylate compound(s) may be influencing thepopulation or metabolic pathways of the microorganisms. Very little (oreven none) of the carboxylate compound may be metabolized by themicroorganisms during the activation period. In these instances, thecarboxylate compound may be acting as a catalyst that activates ametabolic pathway for the production of the metabolic product. Multipleintroductions of the amendment may be made over the course of theactivation period to maintain a concentration level of the amendment inthe formation. Alternatively, the amendment can be pulsed into theformation using discontinuous injections. Experiments demonstratingactivation of methane production with an acetate amendment are describedin the Experimental section below.

Method 200 may also include removing the metabolic product 208 buildingup in the formation as a result of the carboxylate compound amendment.If the metabolic product is a gas such as hydrogen or methane, it may beremoved with conventional natural gas recovery equipment. In someexamples, the products may be removed through the same access pointsthat were used to provide the carboxylate compound to themicroorganisms. In additional examples, the products may be forced outof the formation by injecting a displacement fluid (e.g., nitrogen,water, etc.) into the formation.

Referring now to FIG. 3, a flowchart illustrating a method 300 ofmeasuring the effects of introduced amendments on the production ofmetabolic products from geologic formations is shown. The method 300includes accessing the microorganisms 302 in a carbonaceous materialcontaining geologic formation. Then an analysis of the microorganismformation environment may be conducted, which includes measuring thechemical composition that exists in the environment 304. This mayinclude an in situ analysis of the chemical environment, and/orextracting gases, liquids, and solid substrates from the formation for aremote analysis.

For example, extracted formation samples may be analyzed usingspectrophotometry, NMR, HPLC, gas chromatography, mass spectrometry,voltammetry, and other chemical instrumentation. The tests may be usedto determine the presence and relative concentrations of elements likedissolved carbon, phosphorous, nitrogen, sulfur, magnesium, manganese,iron, calcium, zinc, tungsten, cobalt and molybdenum, among otherelements. The analysis may also be used to measure quantities ofpolyatomic ions such as PO₂ ³⁻, PO₃ ³⁻, and PO₄ ³⁻, NH₄ ⁺, NO₂ ⁻, NO₃ ⁻,and SO₄ ²⁻, among other ions. The quantities of vitamins, and othernutrients may also be determined. An analysis of the pH, salinity,oxidation potential (Eh), and other chemical characteristics of theformation environment may also be performed. Additional details ofchemical analyses that may be performed are described in co-assigned PCTApplication No. PCT/US2005/015259, filed May 3, 2005; and U.S. patentapplication Ser. No. 11/343,429, filed Jan. 30, 2006, of which theentire contents of both applications are herein incorporated byreference for all purposes.

A biological analysis of the microorganisms may also be conducted. Thismay include a quantitative analysis of the population size determined bydirect cell counting techniques, including the use of microscopy, DNAquantification, phospholipid fatty acid analysis, quantitative PCR,protein analysis, etc. The identification of the genera and/or speciesof one or more members of the microorganism consortium by geneticanalysis may also be conducted. For example, an analysis of the DNA ofthe microorganisms may be done where the DNA is optionally cloned into avector and suitable host cell to amplify the amount of DNA to facilitatedetection. In some embodiments, the detecting is of all or part ofribosomal DNA (rDNA), of one or more microorganisms. Alternatively, allor part of another DNA sequence unique to a microorganism may bedetected. Detection may be by use of any appropriate means known to theskilled person. Non-limiting examples include restriction fragmentlength polymorphism (RFLP) or terminal restriction fragment lengthpolymorphism (TRFLP); polymerase chain reaction (PCR); DNA-DNAhybridization, such as with a probe, Southern analysis, or the use of anarray, microchip, bead based array, or the like; denaturing gradient gelelectrophoresis (DGGE); or DNA sequencing, including sequencing of cDNAprepared from RNA as non-limiting examples. Additional details of thebiological analysis of the microorganisms is described in co-assignedU.S. patent application Ser. No. 11/099,879, filed Apr. 5, 2005, theentire contents of which is herein incorporated by reference for allpurposes.

The method 300 also includes providing an amendment to themicroorganisms in the formation 306. Embodiments of the presentinvention include providing amendments of hydrogen, phosphorouscompounds, and/or carboxylate compounds (e.g., acetate) to themicroorganisms. The amendments may also include vitamins, minerals,metals, yeast extracts, and other nutrients. The amendments may stillfurther include water amendments to dilute metabolic inhibitors and/orthe microorganism consortium.

The effect of the amendments can be analyzed by measuring theconcentration of a metabolic intermediary or metabolic product 308 inthe formation environment. If the product concentration and/or rate ofproduct generation does not appear to be reaching a desired level,adjustments may be made to the composition of the amendment 310. Forexample, if an acetate amendment does not appear to be activating themicroorganisms after a set period of time (e.g., 90 days or more), adifferent amendment may be introduced to stimulate the microorganisms(e.g., hydrogen and/or phosphorous compounds).

The method 300 may also include removing the metabolic product 312 fromthe formation. Removal may be triggered when the concentration of thereaction product increases above a threshold level in the formation. Insome of these instances, removal may performed to keep the product in aconcentration range that has been found to stimulate the microorganismsto generate more of the product.

In additional embodiments, removal of the metabolic product may be doneindependently of the product concentration in the formation. Forexample, the reaction products may be continuously removed from theformation as part of a process that cycles the amendment through theformation. The mixture of metabolic products, amendment components andother materials removed from the formation may be processed to separatethe products from components that will be sent back into the formation.

EXPERIMENTAL Hydrogen and Phosphorus Compound Amendments

Experiments were conducted to compare biogenic methane generation fromcoal samples after introducing an amendment of hydrogen gas, aphosphorous compound, and ammonia. For each experiment, methanegeneration from coal samples from the Monarch coal seam in the PowderRiver Basin in Wyoming was periodically measured over the course ofabout 627 days. Each 5 gram coal sample was placed in a 30 ml serumbottle with 15 mL of water that was also taken from the formation. Thecoal and formation water were placed in the serum bottle while workingin an anaerobic glove bag. The headspace in the bottle above the samplewas flushed with a mixture of N₂ and CO₂ (95/5).

Amendments were then added to the samples. In a second set ofexperiments, 4.5 mL of H₂ gas (i.e., 179 μmol of H₂) was added to eachbottle. Also added to the bottles was 0.15 mL of a 2500 mg/L (as N)aqueous ammonium chloride solution to provide a concentration of 25mg/L, as nitrogen, to the samples, and 0.04 mL of a 1800 mg/L potassiumphosphate solution that provided a concentration of 5 mg/L, asphosphate, to the samples. In a second set of experiments, the sameamount of H₂ was added to the bottles, but no ammonium chloride orpotassium phosphate. A third set of experiments introduced the ammoniumchloride and potassium phosphate at the same levels as the first set,but no hydrogen gas was added. The samples were then sealed, removedfrom the glove box, and stored at room temperature over the course ofthe experiments.

The methane levels in the headspace above the samples was periodicallymeasured and recorded. The methane was measured by running samples ofthe headspace gases through a gas chromatograph equipped with a thermalconductivity detector. The highest levels of methane production after627 days occurred in samples treated with an amendment of hydrogen gas,ammonium chloride, and potassium phosphate, with average levels reaching248 μmol of CH₄. This compares with 128 μmol CH₄ for samples just havingthe H₂ amendment, and 64 μmol CH₄ for samples just having the ammoniaand phosphorous compound amendment.

The combination of the hydrogen and potassium phosphate generated moremethane than can be accounted for by methanogenic conversion of theadded hydrogen to methane. In the methanogenic metabolism of hydrogen tomethane, four moles of molecular hydrogen and 1 mole of carbon dioxideare converted into 1 mole of methane:

4H₂+CO₂→CH₄+2 H₂O

This means the 179 μmols of H₂ added to the sample bottles could, atmost, be converted into 44.7 μmols of methane. For samples measuringpeak methane production of 248 μmols, this leaves 203 μmols coming fromother sources. Samples without hydrogen amendments produced about 63μmols of methane from these coal substrates. This still leaves at least185 μmols of methane that was generated from another source.

The source of the additional methane is believed to come from thebiogenic metabolism of the coal into methane. The hydrogen andphosphorous compound amendment is believed to have stimulated themicroorganisms present in the sample to metabolize the coal intomethane. The stimulatory effect of the hydrogen and phosphorousamendment is not limited to enhancing the conversion of the addedhydrogen gas to methane. It also includes stimulating the microorganismsto use methanogenic metabolic pathways that convert the coal substrateinto methane.

Acetate Amendments

Experiments were conducted to measure the effects of acetate amendmentson methane production from samples of carbonaceous materials. Thecarbonaceous materials used in these experiments were coal samples takenfrom underground coal beds at the Monarch coal site. The samples weretransported under anaerobic conditions to 30 ml serum bottles, where 1gram samples of the coal were combined in an anaerobic glove box with 20mL of formation water from the same site and 0.2 mL of cell concentrate.The cell concentrate consisted of cells from about 6.6 L of formationwater added to 15 mL of formation water. The headspace in the bottleabove the sample was exchanged with a mixture of N₂ and CO₂ (95/5).

In a first set of samples, the acetate amendment included adding anaqueous sodium acetate solution to the sample bottles to give thesamples a 10 mg/mL acetate concentration. A second set of controlsamples were prepared in the same manner except for lacking the acetateamendment. Methane levels (measured as a mol. % methane in the headspaceof the sample bottle) were periodically measured in both the amendmentand control samples over the course of 90 days. FIG. 5 shows a plot ofthe methane levels measured in these samples as a function of time.

As FIG. 4 reveals, very little methane generation occurred in either theamendment or control sample during the first 50 days. But themeasurement taken on day 65 shows the methane levels starting to buildin the acetate amendment sample while the control sample continued toshow negligible methane generation. By the 90th day, the acetateamendment sample showed rapid and significant methane generation withmethane representing over 12 mol. % of the headspace in the samplebottles. Meanwhile, the control samples that lacked the acetateamendment still showed almost no methane generation after 90 days.

Plot of FIG. 4 clearly shows that the acetate amendment had asignificant impact on methane generation after an activation period ofabout 65 days. But the plot did not show whether the methane wasproduced by the methanogenic conversion of the acetate into methane, orwhether the methane was derived from the coal sample. Thus, a secondmeasurement was made of the acetate concentration in the samples overthe same period of time.

FIG. 5 shows the plot of the acetate concentrations over time in thesamples. The plot reveals that the acetate concentration did not changesignificantly over the 90 day period. Most significantly, little changein the acetate concentration was observed before and after the methanegeneration rapidly increased in the acetate amendment samples. Thesedata indicate that the acetate amendment acted as an activation agent toenhance the methanogenic metabolism of the coal into methane. The dataalso show that the acetate activation does not occur immediately, andthat a delay of several weeks to months may occur before the start ofsignificant methanogenic activity.

Phosphorous Compound Amendments and Rollover

Rollover is a condition where the rate of biogenic methane productionstarts to plateau as the in situ methane concentration reaches a certainlevel. In many instances, the rate flattens to zero, and the methaneconcentration remains constant over time. The rollover point (i.e., thepoint where the methane concentration begins to break from amonotonically increasing state) can vary between microorganismconsortia, but appears to be reached in almost all unamended samples ofcarbonaceous material that have been examined to date.

But some samples receiving minerals, metals and nutrient amendmentsexhibited less of a rollover effect than unamended controls. Furthertests revealed that the agents responsible for reducing rollover werephosphate compounds, such as sodium or potassium phosphate. FIG. 6 showsa plot of methane levels over time in the headspace of 30 ml serumbottles containing amended and unamended coal samples. The plot for theunamended sample shows the rollover point occurring when the methanelevel in the headspace reaches between 2.5 and 3 mol. %. At thesemethane levels, the rate of methane production starts to decrease andthe methane level remains constant at slightly under 3 mol. %.

A more volatile, but similar pattern was observed for samples treatedwith an ammonium amendment. In these samples, ammonium chloride wasintroduced to give each sample a concentration of 25 mg/L nitrogen atthe start of the methane measurements. The rate of methane production inthese samples was initially greater than for the unamended samples orsamples with other types of amendments (including an amendment ofammonium and phosphate). In addition, the peak methane level in theammonium samples exceeded the peak plateau levels in the unamendedsamples. But eventually the methane levels began to decrease, and byabout day 600 the methane levels in the samples were about the same asthose measured in the unamended samples.

The samples treated with an amendment that included a phosphorouscompound (i.e., potassium phosphate) all appeared to breakthrough theplateau methane level observed in the samples that were prone torollover. As FIG. 6 shows, samples treated with a pure 5 mg/L potassiumphosphate amendment had a methane level of about 4.3 mol. % after 600days, or about 43% higher than samples without phosphate. Amendmentswith ammonium chloride and phosphate did not result in substantialincreases.

FIG. 7 shows another plot of methane concentration over time for sampleswith and without phosphorous compound amendments. Similar to the plot inFIG. 7, this plot shows samples that were not treated with a phosphorousamendment (i.e., a potassium phosphate amendment) reached a rolloverpoint beyond which the methane concentration did not increase. Incontrast, no plateau was observed in the methane concentration of twosets of samples that were treated with a phosphate amendment. At the endof just over 600 days, the phosphate containing samples hadsignificantly higher methane levels than samples treated with a mineralsamendment or the samples that were unamended.

FIGS. 6 and 7 indicate that phosphorous compounds such as potassiumphosphate can extend methanogenesis supported by complex hydrocarbons.Thus, the introduction of a phosphorous compound amendment tomicroorganisms in a geologic formation may stimulate the microorganismsto continue to produce methane in an environment where they are alreadyexposed to high levels of methane.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the microorganism”includes reference to one or more microorganisms and equivalents thereofknown to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

1. A method of stimulating biogenic production of a metabolic productwith enhanced hydrogen content, the method comprising: accessing aconsortium of microorganisms in a geologic formation that includes acarbonaceous material; providing hydrogen to the microorganisms; andproviding phosphorous compound to the microorganism, wherein thecombination of the hydrogen and phosphorous compound stimulates theconsortium to metabolize the carbonaceous material into the metabolicproduct with enhanced hydrogen content.
 2. The method of claim 1,wherein the phosphorous compound comprises a phosphate compound.
 3. Themethod claim 1, wherein the phosphate compound comprises a phosphatesalt.
 4. The method of claim 3, wherein the phosphate compound isselected from the group consisting of sodium phosphate and potassiumphosphate.
 5. The method of claim 1, wherein the phosphorous compoundcomprises a phosphorous oxyacid or a salt of a phosphorous oxyacid. 6.The method of claim 5, wherein the phosphorous oxyacid comprises H₃PO₄,H₃PO₃, or H₃PO₂.
 7. The method of claim 5, wherein the salt of thephosphorous oxyacid comprises dibasic sodium phosphate or dibasicpotassium phosphate.
 8. The method of claim 1, wherein the hydrogen isprovided by injecting hydrogen gas into the geologic formation.
 9. Themethod of claim 1, wherein the hydrogen is provided by introducing acompound to the geologic formation that releases hydrogen gas.
 10. Themethod of claim 9, wherein the compound comprises a hydrogen releasecompound.
 11. The method of claim 9, wherein the compound comprises oneor more lactic acid units.
 12. The method of claim 1, wherein the methodfurther comprises providing a yeast extract to the microorganisms. 13.The method of claim 1, wherein the carbonaceous material comprises coal,oil, carbonaceous shale, oil shale, tar sands, tar, lignite, kerogen,bitumen, or peat.
 14. The method of claim 1, wherein the metabolism ofthe carbonaceous material to the metabolic product comprises one or moreintermediate metabolic steps that produce one or more intermediatemetabolites.
 15. The method of claim 14, wherein the one or moreintermediate metabolites comprise a hydrocarbon selected from the groupconsisting of organic acids, alcohols, amines, straight or branchedalkyl hydrocarbons, and aromatic hydrocarbons.
 16. The method of claim15, wherein the one or more intermediate metabolites is metabolized intothe metabolic product with enhanced hydrogen content.
 17. The method ofclaim 1, wherein the metabolic product with the enhanced hydrogencontent comprises methane or hydrogen.
 18. The method of claim 1,wherein the method further comprises providing a yeast extract amendmentto the microorganisms.
 19. The method of claim 1, wherein the methodfurther comprises providing a vitamin amendment to the microorganisms.20. The method of claim 1, wherein the method further comprisesproviding a trace metal amendment to the microorganisms.
 21. The methodof claim 1, wherein the method further comprises providing a mineralamendment to the microorganisms.
 22. A method of stimulating biogenicproduction of methane, the method comprising: accessing microorganismsin a geologic formation that includes carbonaceous material; providingmolecular hydrogen to the geologic formation using hydrogen gas or ahydrogen release compound; and providing a phosphorous compound to thegeologic formation, wherein the combination of the molecular hydrogenand the phosphorous compound stimulates the microorganisms to metabolizethe carbonaceous material into the methane.
 23. The method of claim 22,wherein the combination of the molecular hydrogen and the phosphorouscompound is an activation agent for the microorganisms to metabolize thecarbonaceous material in the geologic formation into methane.
 24. Themethod of claim 22, wherein the hydrogen release compound comprises apolyacetate ester compound.
 25. The method of claim 22, wherein thehydrogen release compound comprises a polylactate compound.
 26. A methodof stimulating biogenic production of a metabolic product with enhancedhydrogen content, the method comprising: accessing microorganisms in ageologic formation that includes carbonaceous material; detecting adecrease in a production rate of the metabolic product with enhancedhydrogen from the first geologic formation that is indicative of arollover effect; providing molecular hydrogen and a phosphorous compoundto the geologic formation, wherein the molecular hydrogen and thephosphorous compound increase the production rate of the metabolicproduct with enhanced hydrogen content to a level greater than aninflection point where the rollover effect began to occur.
 27. Themethod of claim 26, wherein the rate of production of the metabolicproduct reaches a local maxima due to the rollover effect and themolecular hydrogen and the phosphorous compound increases the rate ofproduction above a level of the local maxima.
 28. The method of claim26, wherein the combination of the molecular hydrogen and thephosphorous compound is an activation agent for the microorganisms tometabolize the carbonaceous material in the geologic formation intomethane.